A pyrotechnic actuator mechanism, which is an actuator mechanism to obtain an output by moving a piston by means of the force of an ignition charge, is used for apparatuses including, for example, an airbag system for vehicles, a pedestrian protection system, a current breaker, a perforator, and a fire extinguishing system. Further, a syringe, which discharges or injects an injection objective substance by means of a pressurized piston, is also known in the field of medical treatment. A pyrotechnic actuator mechanism is widely investigated as a driving source for the syringe as described above. For example, Patent Literature 1 discloses an actuator mechanism which obtains a predetermined output by developing a bellows cup which is expandable as shown in FIG. 1 or a bendable/stretchable cup which is shown in FIG. 6, by means of a combustion product produced by the combustion of an ignition charge.
In the case of the pyrotechnic actuator mechanism as described above, the ignition charge is used as the driving source for the piston. Therefore, any residue is produced to no small extent upon the combustion of the ignition charge. Then, even when the produced residue is in a small amount, it is preferable that the residue is not discharged or emitted to the outside of the actuator mechanism. For example, in the case of a pyrotechnic actuator mechanism shown in Patent Literature 2, a sack (see FIG. 6A), which has been folded up from the beginning, is expanded (see FIG. 6B) by a combustion product produced by the combustion of an ignition charge, and thus an output is obtained for an actuator. In this situation, the combustion product is in a state of being sealed by the sack. Therefore, the combustion product, which contains the residue, hardly leaks out to the outside.
Further, in the case of a pyrotechnic actuator mechanism shown in Patent Literature 3, such a structure is adopted that a piston is extruded by raising the pressure of a gas chamber in accordance with an operation of a gas generator provided on one end side of a cylinder. The movement of the piston is continued until the piston collides with a bush provided in the cylinder. In this case, the clearance is extremely decreased for the cylinder and a main body unit of the piston. However, the combustion residue is not completely prevented from being discharged or emitted to the outside of the cylinder.